Coming up next on the "gma heat index," the huge medi-fast diet. Some people have lost so much weight on it but this seems to be the personal care available for dieters from health professionals and abc's linsey davis is back with that story. Good morning, again, linsey. We interview several who said they tried everything to lose weight, a hot of diets and eating plans and nothing worked until they tried medi weight loss but it does have its crit critics some when question if the methodology is safe. People lose five types more weight using the weight watchers approach. Reporter: We're bombarded by diet strategies often backed by celebrities and images of slip, trim and thin bodies. Self-proclaimed losers of lots of weight. This is a size 20 and these were tight. Reporter: In january markia stone weighed in at 250 pounds. Right now I am 51.7 pounds. She credits her new size 12 figure to a program called medi weight loss, a chain of diet clinics supervised by doctors and register nurses and says it's multiprong ed system has been so questful its 172,000 patients have lost 2.5 million pounds. I lost 190 pounds using it. New patients are given a physical and put on 500 to 700 calories of protein and 200 to 400 calories in fruit, vegetables and healthy weight. By comparison the recommended cal ray range is 2,000 calories a day. Mehdi weightloss suggests supplements and advises them to come in for weekly checkups. For some, appetite suppress apps are recommended. We want them to help them be comfortable when they're on the lower calorie diet and helps them decrease their appetite. Is this safe? Yes, yes. The purpose of the sumps and low calorie/high protein diet is put the body into ketosis which thinks it has to burn its fat to survive. Ketosis, explain. It can activate the body to make you think there is an emergency going on. We don't think being in ketosis over a long period of time is a good thing. Reporter: Mehdi weightloss says it's only used in the acute weight loss and wouldn't be used for more than 12 weeks which dr. Aronne says might be a reasonable option for the dangerous obese. "Allu "allure" featured it in their july issue. jenny craig or weight watchers. With the kind of medically supervised diets that have typically only been available to people of privilege. Reporter: But markia stone says medi weightloss has not only changed her life but become a change of life and is going to shed 31 more pounds. There are 79 medi weightloss clinics. It costs roughly $39 a pound. Markia, if she reaches her goal weight she will have lost 89 pounds and boyce b based on that will spend $3500. She believes it's 100% safe.

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